Up to now, a vehicle image signal processing apparatus that displays a vehicle surrounding image, which is acquired by an imaging device, on a display device is provided. In this case, when an image signal including, for example, a video indicating rear side of a vehicle which is a blind spot of a driver is input from the imaging device, the input image signal is decoded. The video included in the decoded image signal is processed, and the video that has been processed (processed video) is displayed on the display device. In the video processing, guide lines (for example, vehicle width extension lines, etc.), button keys, and so on are drawn for on-screen display in order to display the on-screen drawn video. In recent years, a first control unit and a second control unit are provided for the purpose of dispersing a processing load. In this configuration, when an accessory (ACC) power supply is switched from off to on, the first control unit starts activation firstly, and the second control unit starts activation after the first control unit completes the activation.
In a configuration where the first control unit and the second control unit are provided and the image processing is performed by the second control unit, the processed image cannot be displayed immediately after the accessory power supply is switched from off to on. Regarding this matter, Patent Literature 1 discloses a configuration in which when the accessory power supply is switched from off to on, unprocessed image (raw image) is displayed until the second control unit completes the activation, and the second control unit controls the processed image (image that has been processed) to be displayed after the second control unit completes the activation.
Incidentally, in a decoding unit for decoding the image signal, a setting needs to be carried out for performing the decoding process. In a configuration where the second control unit performs the setting of the decoding unit, the second control unit starts the setting of the decoding unit after the second control unit completes the activation. This leads to such a problem that, during a period before the setting of the decoding unit is completed, even if the second control unit completes the activation, the processed image cannot be displayed and a raw image is forced to be displayed until the setting of the decoding unit is completed.